Fixed displacement piston compressor

ABSTRACT

A compressor includes a rotary shaft, a swash plate, a cylinder block, plural pistons, a crank chamber, a housing, plural passages, a thrust bearing, and an anti-rotation mechanism. The crank chamber accommodates therein the swash plate, and refrigerant of suction pressure is introduced into the crank chamber. The housing is connected to the cylinder block and forms therein a suction chamber and a discharge chamber. The plural passages are provided for communication between the crank chamber and the suction chamber. The thrust bearing is provided between the swash plate and the cylinder block so as to receive thrust load from the swash plate. The thrust bearing has a thrust race located adjacent to the cylinder block. The anti-rotation mechanism is provided for preventing relative rotation of the thrust race to the cylinder block. The anti-rotation mechanism restricts the fluid flow through a specific passage of the plural passages.

BACKGROUND OF THE INVENTION

The present invention relates to a fixed displacement piston compressor having a swash plate in a crank chamber from which refrigerant to be compressed is delivered to a suction chamber through plural passages.

A fixed displacement piston compressor having such plural passages for communication between the crank chamber and the suction chamber and a thrust bearing is known. The thrust bearing is provided between the swash plate and the cylinder block and has a thrust race on the side adjacent to the cylinder block. In such compressor, since the rotation of the thrust race relative to the cylinder block causes wear of the cylinder block due to sliding contact therebetween, it is required to prevent such relative rotation of the thrust race of the thrust bearing to the cylinder block. Additionally, the function of some specific passages among the plural passages is restricted as needed, for example, in order to increase the amount of lubricating oil to be stored in the crank chamber and also to equalize the compression in the respective compression chambers.

A compressor disclosed in Japanese Unexamined Utility Model Application Publication No. 7-10474 has a mechanism for preventing such relative rotation of the thrust race of the thrust bearing to the cylinder block. The compressor has a swash plate inclined to and rotatable around the axis of the rotary shaft of the compressor, a piston disposed at a position spaced radially from the axis of the rotary shaft and reciprocable along the axis with the rotation of the swash plate, and a cylinder block accommodating therein the piston. A thrust bearing is provided between the cylinder block and the swash plate. The thrust race of the thrust bearing adjacent to the cylinder block has a recess, while the cylinder block has a projection engageable with the recess. The engagement of the recess with the projection prevents relative rotation of the thrust race to the cylinder block, thereby preventing wear between thrust race and the cylinder block.

Japanese Unexamined Patent Application Publication No. 2000-297745 discloses another compressor in which the function of some specific passages of the plural passages for delivering refrigerant from the crank chamber to the suction chamber is restricted. In such compressor wherein the suction chamber, from which refrigerant is delivered to plural compression chambers, is connected through the crank chamber to an inlet port that is further connected to an evaporator in an external refrigerant circuit of the compressor, refrigerant is introduced from the inlet port through the crank chamber into the suction chamber. Of the plural passages for delivering refrigerant from the crank chamber to the suction chamber, the passage opened to the crank chamber at a position above the rotary shaft has a flow resistance that is smaller than that of the passage opened to the crank chamber at a position below the rotary shaft. In this case, the amount of refrigerant flowing into the suction chamber through the upper passage is larger than that flowing through the lower passage, which prevents large amount of liquid refrigerant from flowing into the suction chamber.

In the compressor disclosed in Japanese Unexamined Utility Model Application Publication No. 7-10474, however, the recess and the projection in the thrust race of the thrust bearing and the cylinder block, respectively, are provided merely to prevent relative rotation of the thrust race to the cylinder block. On the other hand, in the compressor disclosed in Japanese Unexamined Patent Application Publication No. 2000-297745, a part of the compressor serving as a throttle for restricting the function of the passage is provided merely to offer the same effect as decreasing the diameter of the passage.

The present invention is directed to providing a fixed displacement piston compressor that prevents relative rotation of a thrust race of a thrust bearing to a cylinder block and also restricts the function of a specific passage.

SUMMARY OF THE INVENTION

In accordance with an aspect of the present invention, a fixed displacement piston compressor includes a rotary shaft, a swash plate, a cylinder block, plural pistons, a crank chamber, a housing, plural passages, a thrust bearing, and an anti-rotation mechanism. The swash plate is fixed to the rotary shaft. The cylinder block supports the rotary shaft and has plural cylinder bores arranged around the rotary shaft. The plural pistons are accommodated in the respective cylinder bores. The pistons are coupled to the rotary shaft through the swash plate. The crank chamber accommodates therein the swash plate, and refrigerant of suction pressure is introduced into the crank chamber. The housing is connected to the cylinder block and forms therein a suction chamber and a discharge chamber. The plural passages are provided for communication between the crank chamber and the suction chamber. The thrust bearing is provided between the swash plate and the cylinder block so as to receive thrust load from the swash plate. The thrust bearing has a thrust race located adjacent to the cylinder block. The anti-rotation mechanism is provided for preventing relative rotation of the thrust race to the cylinder block. The anti-rotation mechanism restricts the fluid flow through a specific passage of the plural passages.

Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of a fixed displacement piston compressor according to a first embodiment of the present invention;

FIG. 2A is a cross-sectional view taken along the line IIA-IIA of FIG. 1, showing a thrust race of a thrust bearing of the compressor of FIG. 1;

FIG. 2B is similar to FIG. 2A, but showing the cross section of the compressor with the thrust race removed;

FIG. 3A is a cross-sectional view taken along the line IIIA-IIIA of FIG. 1, showing a thrust race of another thrust bearing of the compressor of FIG. 1;

FIG. 3B is similar to FIG. 3A, but showing the cross section of the compressor with the thrust race removed;

FIG. 4A is a fragmentary sectional view of a fixed displacement piston compressor according to a second embodiment of the present invention; and

FIG. 4B is a front view of a thrust race of a thrust bearing of the compressor of FIG. 4A as viewed from the swash plate of FIG. 4A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a fixed-displacement piston compressor according to the first embodiment of the present invention. It is noted that the left-hand side and the right-hand side as viewed in FIG. 1 are the front side and the rear side of the compressor, respectively, and that the upper and lower sides as viewed in FIG. 1 are the upper and lower sides of the compressor when installed in place, respectively.

The compressor has a pair of cylinder blocks 11 and 12 that are connected to front and rear housings 13 and 16, respectively. The front housing 13 and the rear housing 16 are fastened to the cylinder blocks 11 and 12 using plural bolts 19 (only one is shown in FIG. 1) each of which has an externally threaded end 19A. Each bolt 19 is inserted through bolt holes 13A, 11A and 12A formed in the front housing 13, the cylinder blocks 11 and 12, respectively, so that the threaded end 19A is screwed into a threaded hole 16A formed in the rear housing 16.

The front housing 13 forms therein a discharge chamber 14 and a suction chamber 15, and the rear housing 16 forms therein a discharge chamber 17 and a suction chamber 18. The compressor has a valve port plate 20, a valve plate 22 and a retainer plate 24 interposed between the cylinder block 11 and the front housing 13. The compressor further has a valve port plate 26, a valve plate 28 and a retainer plate 30 interposed between the cylinder block 12 and the rear housing 16.

The valve port plates 20 and 26 are formed with discharge ports 21 and 27, respectively. The valve plates 22 and 28 are formed with discharge valves 23 and 29 that close the discharge ports 21 and 27, respectively. The retainer plates 24 and 30 are formed with retainers 25 and 31 that regulate the opening of the discharge valves 23 and 29, respectively.

The cylinder blocks 11 and 12 are formed therethrough with shaft holes 34 and 35, respectively, and a rotary shaft 32 is inserted through the shaft holes 34 and 35 and rotatably supported by the cylinder blocks 11 and 12. A seal member 33 is interposed between the front housing 13 and the rotary shaft 32. The front housing 13, the rotary shaft 32 and the seal member 33 cooperate to define a space 48 that is connected to the suction chamber 15 through a passage 13B. The compressor has a swash plate 36 fixed on the rotary shaft 32 for rotation therewith. The swash plate 36 is accommodated in a crank chamber 37 that is formed by and between the cylinder blocks 11 and 12.

A thrust bearing 46 is disposed between an annular base 36A of the swash plate 36 and the end surface 11 B of the cylinder block 11, and a thrust bearing 47 is disposed between the base 36A of the swash plate 36 and the end surface 12B of the cylinder block 12.

The cylinder block 11 is formed with an inlet port 38 through which the crank chamber 37 communicates with an external refrigerant circuit (not shown). The cylinder block 11 is formed therethrough with plural passages 39 (see FIGS. 2A and 2B) that connect the crank chamber 37 to the suction chamber 15 of the front housing 13, and similarly the cylinder block 12 is formed therethrough with plural passages 49 (see FIGS. 3A and 3B) that connect the crank chamber 37 to the suction chamber 18 of the rear housing 16.

Referring to FIGS. 2A, 2B, 3A and 3B, the cylinder block 11 is formed with plural cylinder bores 40 arranged around the rotary shaft 32, and the cylinder block 12 is formed similarly with plural cylinder bores 50 arranged around the rotary shaft 32. Each cylinder bore 40 is paired with its opposite cylinder bore 50 to accommodate therein a double-headed piston 44. The front end of the double-headed piston 44 defines a compression chamber 41 in the cylinder bore 40, and the rear end of the double-headed piston 44 defines a compression chamber 51 in the cylinder bore 50. The swash plate 36 has a pair of shoes 45 for each piston 44 for transmitting the rotating motion of the swash plate 36 to the piston 44.

A part of the inner peripheral surface of the shaft hole 34 which is in contact with the rotary shaft 32 serves as a sealing surface 42, and a part of the inner peripheral surface of the shaft hole 35 which is in contact with the rotary shaft 32 also serves as a sealing surface 52. The diameter of circles described by the sealing surfaces 42 and 52 of the shaft holes 34 and 35 is smaller than that of other parts of the shaft holes 34 and 35. Therefore, the rotary shaft 32 is supported directly on the sealing surfaces 42 and 52 of the cylinder blocks 11 and 12.

A supply passage 54 is formed in the rotary shaft 32 so as to extend in the longitudinal direction of the compressor. The supply passage 54 is opened at the rear end of the rotary shaft 32 to the suction chamber 18 in the rear housing 16. The rotary shaft 32 is formed with passages 55 and 56 that communicate with the supply passage 54.

The cylinder block 11 is formed with plural passages 43 (only one is shown in FIG. 1) that are communicable with their associated cylinder bores 40 and the shaft hole 34. The passage 43 has an inlet 43A that is opened on the sealing surface 42 and intermittently communicable with the outlet 55A of the passage 55 as the rotary shaft 32 rotates.

The cylinder block 12 is formed with plural passages 53 (only one is shown in FIG. 1) that are communicable with their associated cylinder bores 50 and the shaft hole 35. The passage 53 has an inlet 53A that is opened on the sealing surface 52 and intermittently communicable with the outlet 56A of the passage 56 as the rotary shaft 32 rotates.

A part of the rotary shaft 32 that is surrounded by the sealing surfaces 42 and 52 serves as a rotary valve. The rotary shaft 32 has ports 57 and 58 in the periphery thereof. The ports 57 and 58 are radially aligned with passages 60 and 61, respectively, which are formed through the base 36A of the swash plate 36. The supply passage 54 of the rotary shaft 32 communicates with the crank chamber 37 through the ports 57 and 58 and the passages 60 and 61. The rotary shaft 32 is formed with a passage 59 that connects the supply passage 54 to the space 48.

The thrust bearing 46 has a ring-shaped thrust race 62 adjacent to the base 36A of the swash plate 36, a ring-shaped thrust race 63 adjacent to the end surface 11B of the cylinder block 11 and a plurality of cylindrical rollers 64 provided between the thrust races 62 and 63. The thrust bearing 47 has a ring-shaped thrust race 65 adjacent to the base 36A of the swash plate 36, a ring-shaped thrust race 66 adjacent to the end surface 128 of the cylinder block 12 and a plurality of cylindrical rollers 67 provided between the thrust races 65 and 66.

In the present embodiment, as shown in FIGS. 2A and 3A, the compressor has anti-rotation mechanisms 70 and 71 for preventing the thrust race 63 of the thrust bearing 46 from rotating relative to the cylinder block 11, and anti-rotation mechanisms 80 and 81 for preventing the thrust race 66 of the thrust bearing 47 from rotating relative to the cylinder block 12.

FIG. 2A shows the thrust race 63 of the thrust bearing 46 adjacent to the cylinder block 11, and FIG. 2B is similar to FIG. 2A with the thrust race 63 removed from the cylinder block 11. In the drawings, the double-headed pistons 44 are not illustrated for simplification. As shown in the drawings, the opening of each passage 39 to the crank chamber 37 is located around the thrust race 63, and the thrust race 63 has two projections 72 and 73 formed in the periphery thereof so as to extend radially outward over the openings of the specific passages 39 of the plural passages 39. The projection 72 restricts the fluid flow through the passage 39 that is closest to the inlet port 38 of the plural passages 39. The projection 73 restricts the fluid flow through the passage 39 whose position is lowest of the plural passages 39 when the compressor is installed in place in a vehicle (the passage 39 whose position is lowest in FIG. 2). Specifically, the specific passage 39 associated with the projection 73 is one whose opening to the crank chamber 37 is located at the lowest position as viewed in vertical direction when the compressor is installed in a vehicle, and the specific passage 39 associated with the projection 72 is one whose opening to the crank chamber 37 is located closest to the inlet port 38. There is provided a gap between the opening of the specific passage 39 and the projection 72 (73) of the thrust race 63 of the thrust bearing 46 (see FIG. 1).

The cylinder block 11 has a pair of retainers 74 and a pair of retainers 75 projecting from the end surface 11B of the cylinder block 11 toward the swash plate 36. The retainers 74 are located on opposite sides of the projection 72 as viewed in the rotating direction of the rotary shaft 32, and similarly the retainers 75 are located on opposite sides of the projection 73 as viewed in the rotating direction of the rotary shaft 32. The movement of the projections 72 and 73 in the rotating direction of the rotary shaft 32 is prevented by the retainers 74 and 75, so that the rotation of the thrust race 63 on the axis P of the rotary shaft 32 is restricted. The projections 72 and 73 cooperate with their associated retainers 74 and 75 to serve as the anti-rotation mechanism 70 and 71, respectively.

FIG. 3A shows the thrust race 66 of the thrust bearing 47 adjacent to the cylinder block 12, and FIG. 3B is similar to FIG. 3A with the thrust race 66 removed from the cylinder block 12. In the drawings, the double-headed pistons 44 are not illustrated for simplification. As shown in the drawings, the opening of each passage 49 to the crank chamber 37 is located around the thrust race 66, and the thrust race 66 has two projections 82 and 83 formed in the periphery thereof so as to extend radially outward over the openings of the specific passages 49 of the plural passages 49. The projection 82 restricts the fluid flow through the passage 49 that is closest to the inlet port 38 of the plural passages 49. The projection 83 restricts the fluid flow through the passage 49 whose position is lowest of the plural passages 49 when the compressor is installed in place in a vehicle (the passage 49 whose position is lowest in FIG. 3). Specifically, the specific passage 49 associated with the projection 83 is one whose opening to the crank chamber 37 is located at the lowest position as viewed in vertical direction when the compressor is installed in a vehicle, and the specific passage 49 associated with the projection 82 is one whose opening to the crank chamber 37 is located closest to the inlet port 38. There is provided a gap between the opening of the specific passage 49 and the projection 82 (83) of the thrust race 66 of the thrust bearing 47 (see FIG. 1).

The cylinder block 12 has a pair of retainers 84 and a pair of retainers 85 projecting from the end surface 12B of the cylinder block 12 toward the swash plate 36. The retainers 84 are located on opposite sides of the projection 82 as viewed in the rotating direction of the rotary shaft 32, and similarly the retainers 85 are located on opposite sides of the projection 83 as viewed in the rotating direction of the rotary shaft 32. The movement of the projections 82 and 83 in the rotating direction of the rotary shaft 32 is prevented by the retainers 84 and 85, so that the rotation of the thrust race 66 on the axis P of the rotary shaft 32 is restricted. The projections 82 and 83 cooperate with their associated retainers 84 and 85 to serve as the anti-rotation mechanism 80 and 81, respectively.

In the above-described compressor, when the rotary shaft 32 is rotated with the swash plate 36 by the driving force from a drive source not shown, the rotating motion of the swash plate 36 is transmitted to the double-headed pistons 44 through the shoes 45, so that each double-headed piston 44 reciprocates in its associated cylinder bores 40 and 50. Refrigerant of suction pressure is introduced from the external refrigerant circuit through the inlet port 38 into the crank camber 37 and then flows through the passages 60 and 61 and the ports 57 and 58 into the supply passage 54. Part of the refrigerant introduced into the crank chamber 37 is delivered through the passages 39 and 49 to the suction chambers 15 and 18. The refrigerant in the suction chamber 15 is introduced through the passage 13B, the space 48 and the passage 59 into the supply passage 54. The refrigerant in the suction chamber 18 is introduced directly into the supply passage 54.

When the double-headed piston 44 is in the suction stroke for the cylinder bore 40, that is, when the double-headed piston 44 is moving rightward in FIG. 1, the outlet 55A of the passage 55 is connected to the inlet 43A of the passage 43. Refrigerant in the passage 54 of the rotary shaft 32 is introduced through the passages 55 and 43 into the compression chamber 41 in the cylinder bore 40.

When the double-headed piston 44 is in the discharge stroke for the first cylinder bore 40, that is, when the double-headed piston 44 is moving leftward in FIG. 1, the outlet 55A of the passage 55 is disconnected from the inlet 43A of the passage 43. Refrigerant in the compression chamber 41 is discharged into the discharge chamber 14 through the discharge port 21 while pushing open the discharge valve 23. The refrigerant discharged into the discharge chamber 14 then flows into the external refrigerant circuit. The refrigerant flowed through the external refrigerant circuit then returns through the inlet port 38 to the crank chamber 37.

When the double-headed piston 44 is in the suction stroke for the cylinder bore 50, that is, when the double-headed piston 44 is moving leftward in FIG. 1, the outlet 56A of the passage 56 is connected to the inlet 53A of the passage 53. Refrigerant in the passage 54 of the rotary shaft 32 is introduced through the passages 56 and 53 into the compression chamber 51 in the cylinder bore 50.

When the double-headed piston 44 is in the discharge stroke for the cylinder bore 50, that is, when the double-headed piston 44 is moving rightward in FIG. 1, the outlet 56A of the passage 56 is disconnected from the inlet 53A of the passage 53. Refrigerant in the compression chamber 51 is discharged into the discharge chamber 17 through the discharge port 27 while pushing open the discharge valve 29. The refrigerant discharged into the discharge chamber 17 flows into the external refrigerant circuit. The refrigerant flowed through the external refrigerant circuit then returns through the inlet port 38 to the crank chamber 37.

While the compressor is in operation and the swash plate 36 is rotating with the rotary shaft 32, the thrust bearings 46 and 47 support the thrust load from the swash plate 36. In this case, although the thrust race 63 of the thrust bearing 46 not only supports the thrust load but also receives a force acting in the rotating direction of the rotary shaft 32, the projections 72 and 73 of the thrust race 63 are brought into contact with the retainers 74 and 75, respectively, thereby restricting the rotation of the thrust race 63. Thus, the anti-rotation mechanisms 70 and 71 prevent the thrust race 63 of the thrust bearing 46 from rotating relative to the cylinder block 11.

Flow of refrigerant through the passage 39 that is closest to the inlet port 38 is restricted the projection 72 of the thrust race 63, so that the function of such passage 39 is restricted. This prevents the refrigerant introduced through the inlet port 38 into the crank chamber 37 from flowing concentratedly through the passage 39 that is closest to the inlet port 38, so that the amount of the refrigerant flowing through the passages 39 is made uniform. On the other hand, the flow through the passage 39 whose position is lowest is restricted by the projection 73 of the thrust race 63, so that the function of such passage 39 is restricted. This makes it difficult for the lubricating oil stored in the crank chamber 37 to flow through such passage 39 into the suction chamber 15.

Similarly, although the thrust race 66 of the thrust bearing 47 not only supports the thrust load but also receives a force acting in the rotating direction of the rotary shaft 32, the projections 82 and 83 of the thrust race 66 are brought into contact with the retainers 84 and 85, respectively, thereby restricting the rotation of the thrust race 66. Thus, the anti-rotation mechanisms 80 and 81 prevent the thrust race 66 of the thrust bearing 47 from rotating relative to the cylinder block 12.

Flow of refrigerant through the passage 49 that is closest to the inlet port 38 is restricted the projection 82 of the thrust race 66, so that the function of such passage 49 is restricted. This prevents the refrigerant introduced through the inlet port 38 into the crank chamber 37 from flowing concentratedly through the passage 49 that is closest to the inlet port 38, so that the amount of the refrigerant flowing through the passages 49 is made uniform. On the other hand, the flow through the passage 49 whose position is lowest is restricted by the projection 83 of the thrust race 66, so that the function of such passage 49 is restricted. This makes it difficult for the lubricating oil stored in the crank chamber 37 to flow through such passage 49 into the suction chamber 18.

The compressor according to the first embodiment offers the following advantages.

-   -   (1) The anti-rotation mechanisms 70, 71, 80, 81 not only prevent         the thrust races 63, 66 of the thrust bearings 46, 47 adjacent         to the cylinder blocks 11, 12 from rotating relative to the         cylinder blocks 11, 12, but also restrict the fluid flow through         the specific passages 39, 49 of the plural passages 39, 49. This         prevents wear due to the relative rotation of the thrust races         63, 66 to the cylinder blocks 11, 12, as well as preventing the         reduction of the performance of the compressor or refrigeration         cycle by restricting the function of the specific passages 39,         49.     -   (2) The amount of the refrigerant flowing through the passages         39, 49 closest to the inlet port 38 tends to be larger than that         flowing through the other passages 39, 49 located further away         from the inlet port 38. Flow through the passages 39, 49 closest         to the inlet port 38 is restricted by the anti-rotation         mechanisms 70, 71, 80, 81. Thus, the amount of refrigerant         flowing through the plural passages 39, 49 is made uniform,         resulting in a smaller difference in efficiency of compression         among the respective cylinder bores.     -   (3) Since the anti-rotation mechanisms 70, 71, 80, 81 restrict         the fluid flow through the passages 39, 49 whose position is         lowest as viewed in the vertical direction, lubricating oil         stored in the lower region of the crank chamber 37 is restricted         from flowing through such passages 39, 49. Thus, the amount of         lubricating oil to be stored in the crank chamber 37 is         increased, resulting in reduced amount of lubricating oil         flowing into the external refrigerant circuit and also         preventing reduction of efficiency of heat exchanging in the         refrigeration cycle.     -   (4) The projections 72, 73, 82, 83 of the thrust races 63, 66,         which serve to restrict the fluid flow through the specific         passages 39, 49, are restricted from moving by the retainers 74,         75, 84, 85 of the cylinder blocks 11, 12, so that relative         rotation of the thrust races 63, 66 to the cylinder blocks 11,         12 is prevented. The prevention of the relative rotation of the         thrust races 63, 66 to the cylinder blocks 11, 12 may be         accomplished only by providing such simple projections 72, 73,         82, 83 on the thrust races 63, 66 and the retainers 74, 75, 84,         85 on the cylinder blocks 11, 12. The projections 72, 73, 82, 83         restrict the fluid flow through the specific passages 39, 49 to         restrict the function of such passages 39, 49.

FIGS. 4A and 4B show the second embodiment of the present invention. The second embodiment differs from the first embodiment in the structure of the anti-rotation mechanism. In the drawings, same reference numerals are used for the common elements or components in the first and second embodiments, and the description of such elements or components for the second embodiment will be omitted.

As shown in FIGS. 4A and 4B, the anti-rotation mechanism 90 is provided by a projection 92, a pin 94 and the passage 39. The projection 92 is formed in the periphery of the thrust race 91 adjacent to the cylinder block 11 so as to project radially outward. The projection 92 is formed therethrough with a hole 93 in which the pin 94 is mounted by press fitting. The diameter of the pin 94 is set so that the pin 94 is inserted in the opening of the passage 39. The thrust bearing is positioned so that its thrust race 91 faces the end surface 11B of the cylinder block 11 with the pin 94 inserted in the opening of the passage 39 whose position is lowest.

With the anti-rotation mechanism 90 of the second embodiment, although force is applied to the thrust race 91 in the rotating direction of the rotary shaft 32 while the compressor is operating, the pin 94 inserted in the opening of the passage 39 restricts the movement of the projection 92 of the thrust race 91, so that the rotation of the thrust race 91 on the axis P is prevented. The pin 94 inserted in the opening of the specific passage 39 whose position is lowest restricts the fluid flow through such passage 39 and the function thereof. In the second embodiment, the pin 94 may be inserted not in the opening of the passage 39 at the lowest position, but in the opening of the passage 39 closest to the inlet port 38. Alternatively, the thrust race 91 may have two projections each having a pin, such as the projection 92 and the pin 94, so that one of the pins is inserted in the opening of the passage 39 whose position is lowest and the other pin is inserted in the opening of the passage 39 closest to the inlet port 38. Further, an anti-rotation mechanism such as the anti-rotation mechanism 90 may be provided for the thrust race of the thrust bearing adjacent to the cylinder block 12.

According to the second embodiment, the end surfaces 11B, 12B of the cylinder blocks 11, 12 do not require projections such as the retainers 74, 75, 84, 85 in the first embodiment, and the opening of the passages 39, 49 in which the pin 94 is inserted may be freely selected. Thus, even when the position of the compressor around the axis P of the rotary shaft 32 is changed, for example, when the lowermost passages 39, 49 are changed depending on the type of vehicles, the fluid flow through the passages 39, 49 located at the lowest position is restricted regardless of the type of vehicles.

The above embodiments may be modified in various ways as exemplified below.

Although in the first embodiment the anti-rotation mechanism restricts the flow through the passage closest to the inlet port and also through the passage whose position is lowest, either one of these two passages may be restricted. The inlet port for introducing refrigerant into the crank chamber may be provided on any side of the cylinder block other than the bottom. The first embodiment of the anti-rotation mechanism may be combined with the second embodiment of the anti-rotation mechanism to restrict the flow through the plural passages.

Although in the first embodiment the projection of the thrust race restricts the flow through the passage, it may close the passage so that no refrigerant flow is allowed. Although in the first embodiment there is provided a gap between the projection of the thrust race and the opening of the specific passage, the size of the gap may be changed depending on the direction or degree of the thrust load so that the projection serves as a variable throttle.

Although in the second embodiment the thrust race is provided separately from the pin, they may be provided integrally, which results in reduced number of parts of the compressor. Further, the cross section of the pin may be of any shape as far as the pin serves to restrict the flow through the passage. The shape includes, for example, a circle, a polygon and a semicircle.

Although in the first and second embodiments the present invention is applied to a compressor having a rotary shaft serving also as a rotary valve, it may be applied to a compressor having a valve port plate formed with a suction port closed by a suction valve. In this case, the passage connecting the crank chamber to the suction chamber serves as a main passage for delivering refrigerant to be compressed. 

1. A fixed displacement piston compressor, comprising: a rotary shaft; a swash plate fixed to the rotary shaft; a cylinder block supporting the rotary shaft, the cylinder block having plural cylinder bores arranged around the rotary shaft; plural pistons accommodated in the respective cylinder bores, the pistons being coupled to the rotary shaft through the swash plate; a crank chamber into which refrigerant of suction pressure is introduced, the crank chamber accommodating therein the swash plate; a housing connected to the cylinder block and forming therein a suction chamber and a discharge chamber; plural passages for communication between the crank chamber and the suction chamber; a thrust bearing provided between the swash plate and the cylinder block so as to receive thrust load from the swash plate, the thrust bearing having a thrust race located adjacent to the cylinder block; and an anti-rotation mechanism for preventing relative rotation of the thrust race to the cylinder block, the anti-rotation mechanism restricting the fluid flow through a specific passage of the plural passages.
 2. The fixed displacement piston compressor according to claim 1, wherein the specific passage is one whose opening to the crank chamber is located at the lowest position as viewed in vertical direction when the compressor is installed in a vehicle.
 3. The fixed displacement piston compressor according to claim 1, further comprising an inlet port through which refrigerant of suction pressure is introduced into the crank chamber, wherein the specific passage is one whose opening to the crank chamber is located closest to the inlet port.
 4. The fixed displacement piston compressor according to claim 1, wherein each passage is formed in the cylinder block, and the opening of each passage to the crank chamber is located around the thrust race.
 5. The fixed displacement piston compressor according to claim 4, wherein the anti-rotation mechanism includes a projection formed in the periphery of the thrust race so as to extend radially outward and a retainer formed in the cylinder block so as to restrict movement of the projection, and the projection is located at a position over the opening of the specific passage.
 6. The fixed displacement piston compressor according to claim 5, wherein there is provided a gap between the opening of the specific passage and the projection.
 7. The fixed displacement piston compressor according to claim 5, wherein a pair of the retainers is formed in the cylinder block so as to project toward the swash plate, and the retainers are located on opposite sides of the projection as viewed in rotating direction of the rotary shaft so that the projection is brought into contact with the retainers.
 8. The fixed displacement piston compressor according to claim 4, wherein the anti-rotation mechanism includes a projection formed in the periphery of the thrust race so as to extend radially outward and a pin mounted to the projection, the pin being inserted in the opening of the specific passage. 